VARIATION IN PYRONE PRODUCTION, LYTIC ENZYMES AND CONTROL OF RHIZOCTONIA ROOT-ROT OF WHEAT AMONG SINGLE-SPORE ISOLATES OF TRICHODERMA-KONINGII

Fifty-four single-spore isolates were obtained from two wheat field st rains of Trichoderma koningii. These isolates inhibited the growth of Rhizoctonia solani to varying levels when tested on potato dextrose ag ar. 6-Pentyl-alpha-pyrone was isolated only from the extracts obtained from those isolates which showed strong inhibition of the pathogen on agar. Six isolates, three pyrone producers and three non-producers, w ere tested for protection of wheat against rhizoctonia root rot under controlled conditions. Only the pyrone producers significantly reduced root rot when applied to the soil and incubated for 14 d with the pat hogen before planting. Those not producing pyrone did not reduce the d isease when applied to the soil either with or without an incubation p eriod in soil. There was no relationship between the disease protectio n ability of the isolates and their mycoparasitic ability or their pro duction of chitinase, glucanase, cellulase or xylanase. This indicates that the pyrone antibiotic may have an import-ant role in the reducti on of rhizoctonia root rot of wheat by the effective strains and that the ability to produce the antibiotic may vary among asexually produce d progenies.